This invention relates to new and improved apparatus and methods for tracing electrical conductors of both alternating and direct current electrical power, and more specifically it pertains to identifying circuit breakers, fuses, switches and other current conducting or handling devices connected to a source of electrical power.
It is oftentimes necessary to trace and identify particular circuits and electrical devices in a power distribution network, such as circuit breakers or fuses. Identification has typically been accomplished by practicing one or two manual techniques. One technique is to selectively disrupt power by opening the circuit breakers one at a time. When power is no longer present at the circuit, electrical device or feeder conductor in question, the opened circuit breaker identifies the item in question. The disadvantage to this technique is that electrical power is temporarily disconnected from each of the circuits and branch conductors in the course of the search, and it may be critical to maintain power to some of these circuits and branch conductors. Critical circuits include those which supply power to hospital equipment, computers, and many other types of sensitive electronic equipment. Another disadvantage is that a considerable amount of time is consumed in selectively and individually opening each of the circuit breakers. The second manual technique of identifying a circuit breaker is to introduce a sufficiently high electrical current load on the particular branch conductor to trip the circuit breaker or open the fuse. This technique is typically achieved by introducing an intentional short circuit to the branch conductor. The disadvantage of this technique is that the power will then be totally disrupted, creating the detrimental consequences previously mentioned. The increased current drawn by the short circuit can create dangerous momentary overheating or fire conditions or can cause larger trunk or distribution breakers to trip open at the same time the branch circuit breaker is tripped open. Of course, once a distribution breaker trips open, a large number of branch and distribution conductors will be disconnected from the source of electrical power.
A variety of test instruments are also available for testing and determining a variety of different electrical conditions including tracing and identifying feeder conductors, circuit breakers and other current conducting devices as well as tracing and identifying short circuited conductors. Certain of these prior art devices require interruption of power to the conductors in order to accomplish the tracing and identification. Other types of prior art devices employ means which cyclically create a current load on a particular conductor of sufficient magnitude to allow the increased current load, and hence the electrical device, to be identified with a conventional ammeter or impedence measuring device. Still other types of prior art devices introduce a relatively high-frequency signal on the conductor while conventional power is maintained and high-frequency signal is inductively detected. The high-frequency signal detection apparatus offers the best potential for reliable and simple circuit identification and detection, but such prior art devices are typically subject to adverse and detrimental influences, such as false signals resulting from spurious signals from transients and switching currents, reduced sensitivity for detecting and identifying the desired feeder conductors through panel enclosures and tubular conduits, and a somewhat limited specificity in isolating one particular conductor from a number of other conductors located in close proximity. Other disadvantages of such prior art systems and methods are known to those appreciating this particular field and its problems, and will be made more particularly apparent with comprehension of the desirable features of the present invention.